<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 一类标签 */
    /* div {
      background-color: red;
    } */

    /* 类选择器 . */
    /* .one {
      background-color: red;
    }

    .two {
      background-color: yellow;
    } */



    /* 后代 */
    /* .one p button {
      background-color: yellow;
    } */

    /* 悬停 伪类选择器 */
    /* 只有鼠标悬停时才生效 */
    button:hover {
      background-color: red;
      width: 100px;
      font-size: 50px;

      /* 鼠标图标 手指 */
      cursor: pointer;
    }

    /* 被点击  */
    div :active {
      background-color: yellow;
    }
  </style>
</head>

<body>
  <div>234</div>
  <!-- <div class="one">div1</div>
  <div class="two">div2</div>
  <div class="one two">div3</div> -->



  <!-- <button>普通按钮</button>
  <div>
    <button>div 后代的按钮</button>
  </div>
  <div class="one">
    <p>
      <button>div 后后代</button>
    </p>
  </div> -->


  <button>登录</button>
</body>

</html>